Arc chute utilizing interleaved u-shaped conductive members



March 17, 1953 A. E. HERMAN ARC CHUTE UTILIZING INTERLEAVED U-SHAPED CONDUCTIVE MEMBERS Filed June 29, 1950 2 SHEETSSHEET l March 17, 1953 A. E. HERMAN ARC CHUTE UTILIZING INTERLEAVED U-SI-IAPED CONDUCTIVE MEMBERS 7 2 SHEETSSHEET 2 Filed June 29, 1950 Patented Mar. 17, 1953 ARC CHUTE UTILIZING INTERLE VED U-SHAPED CONDUCTIV-E MEMBERS Alvin E. Herman, Milwaukee, Wis. assignor to Allis-Chalmers Manufacturing Company, Milwaukee, Wis.

Application June 29, 1950, Serial No. 171,074 Claims. (01. 200-444) 1 r This invention relates in general to are extin guishing means and in particular to are chutes associated with electric switching devices.

It is a principal object of this invention to provide an arc extinguishing structure in which series connected arcs are successively drawn and each of the arcs is subsequently broken into a plurality of divided arcs.

It is an additional object of this invention to provide an improved arc extinguishing chute in which the arc current traverses a path of increasing resistance as the arc travels in the chute.

It is a further object of the present invention to provide an arc extinguishing chute assembly which is compact, rugged "and easily detached from the switching device.

Objects and advantages other than those outlined above will be readily apparent from the following detailed description when read in connection with the accompanying drawings, in which:

Fig. 1 is a side view, partly broken away, of a switching device embodying the present invention;

Fig. 2 is a sectional view taken along line II-II of Fig. 1;

Fig. 3 is a side View of the arc chute assembly of the present invention, with one side wall removed;

Fig. 4 is a sectional view taken along line IV-IV of Fig. 3;

Fig. 5 is a development view on an enlarged scale looking in the direction of arrow V of Fig. 3;

Fig. 6 is a perspective view of a component element of the arc chute assembly;

Fig. 7 is an end view of an alternate embodiment of a component element of the arc chute assembly;

Figs. 8, 9 and 10 are diagrammatic views along a median plane of the arc chute illustrating successive steps in the operation of the arc chute of this invention as the contacts of the switching device separate.

Referring to the drawings, a switching device embodying the present invention comprises a pair of relatively movable contacts H, [2 between which an arc may be formed upon separation thereof. The are may be drawn in any suitable insulating fluid, such as air at atmospheric pressure. Contact H is connected through a curved conductive bar [3 to a terminal stud 14, while contact I2 is connected through a conductive member l5 and a flexible lead It to a terminal stud ll. Studs 14, I! represent connections to a circuit which the switching device is to interrupt.

The fixed contact assembly is secured to a suit-- '2 able insulating base it by nuts 19 engaging terminal studs [4 and by a bracket 22 secured to bar i3 by a bolt 23,, while stud I7 is secured to base 8 by nuts 20. Secured to bar l3 by rivets 21 is a U-shaped bridging member 23 of laminated ma netic material which has a pair of laminated polev plates SI, 32 secured to its legs by rivets 33. Bar !3 acts as a blowout coil in a well known manner, in cooperation with member 28 and plates 3 I, 32,; to accelerate the travel of the are formed upon separation of contacts ll, 12 into the arc extinguishing chute. The additional blowout actionprcvided by bar l3, member 28 and plates 3|, 32 may be dispensed with if the heat generated by the arc is sufficient to impel the arc upwardly in the chute.

Contact 92 is movable into and out of engagementwith contact H by movement of a shaft 35. Shaft 36 is journaled in brackets 31 secured to base It by screws 33 and is given rotational movement by suitable actuating means (not shown) such as an electromagnet. Shaft 36 is provided with an octagonal portion 39 having an insulating coating 4!. Around octagonal portion 39 is secured a clamp comprising a pair of clamping members 42-, 43 secured together by screws 44. Clamping member 42 is provided with an extension forming a finger 46 bearing against member I5 and providing a pivot about which member l5 and contact [2 may turn. A plate 45, of suitable,

known hard material such as stainless steel, is provided to furnish a wearing surface for finger 45. Flexible lead it is clamped against nut 20 and stud I! by a nut 2-4.

A stud 41 extends with clearance through an aperture in member 42 and is secured to member I5 and flexible lead It by a. nut 48. A spring 4}) compressed between finger 46 and a nut 5| pulls against member l5 and urges contact l2 to the closed position shown when finger 46 is in the position shown. Nuts 5| may be adjusted to vary the pressure between contacts I l l2. v

Whenshaft 36; is rotated clockwise from the position shown, finger 46' also rotates clockwise and enables spring 49 to pull member l5 and con-- tact 52 to the right, thereby separating contacts.

ll, l2 and causing an arc tobe formed between the contacts. The heat generated by formationof the arc impels the arc to rise into the are ex t'in'guishing chute 55, and an additional impellin'g force may be given to the are by the blowout as zen'lsbzly comprising bar l3, member 28 and plates As best shown in Figs. 3 to 5, the arc chute 55 comprises a pair of spaced side walls 56, 5'! lo cated on opposite sides of the path of movement of the arc. Chute 55 is provided with an intermediate section 53 adjacent contacts l2 wherein the arc is formed and an exhaust section 54 between the top portions of the side walls 55, 51. Two pluralities of U-shaped conductive members 58a through 58] and 59a, through 59f are secured to side walls 56, 51, respectively, and form two interleaved rows disposed in the general lengthwise direction of the arc. Members 58, 59 may be made of any suitable heat resistant conductor such as steel or brass. As shown in Fig. 6 which illustrates a representative member, 586, each conductive member 58, 59 comprises a pair of spaced leg portions 6 62 extending in the general direction of travel of the arc and a curved portion 63 joining the leg portions 6|, 62 in the intermediate section of the chute. The distance between adjacent leg portions of adjacent conductive members may be of any suitable value but preferably increases from the intermediate section to the exhaust section of the chute 55, as shown in Fig. 3. The distance between leg portions 6|, 62 may be constant or, as shown in Fig. 3, may be greatest at the bight of U and decrease as the leg portions approach the exhaust section of the chute.

Members 58, 59 abut their respective side walls along an edge extending from the bight of the U to the exhaust section of the chute. Some of the conductive members 58, 59, and referably all of them, increase in depth in a direction perpendicular to the direction of movement of the arc and to the lengthwise direction of the are, i. e. away from the side wall to which they are secured and toward the opposite side wall, from the bight of the U, and are adjacent to or abut the opposite side wall at the exhaust section of the chute. This increase in depth of members 58, 59 forms edges 69 on members 58, 59 upon which the arc impinges durin its movement in chute 55. As shown in the drawing, members 58, 59 may be set in recesses 64 in their respective side walls 56, 51, and if members 58, 59 abut the opposite side wall at the exhaust section of the chute, recesses 65 may be provided to receive the abutting ends.

Insulating end members 66, 61 are provided to maintain the proper spacing of side walls 56, 51, and to cooperate with the side walls to confine the arc. The entire arc chute assembly is rigidly secured together by rivets 68 extending through walls 56, 51 and members 66, 61. A bracket 1| secured to bridging member 28 by rivets 12 is provided to removably mount the arc chute assembly with respect to contacts l1, 12. Projecting fingers 13 of bracket 1| engage a pair of recesses 14, 15 in side walls 56, 51 when the arc chute assembly is lowered to the position shown in Fig. 1. Figures 73 abut stepped portions 16, 11 of side walls 56, 51 above recesses 14, 15 to thereby detachably secure the chute assembly. Pole plates 3|, 32 engage recesses 18, 19 in side walls 56, 51 and abut the side walls above these recesses to provide additional support for the arc chute assembly.

Upon separation of contacts I2, an arc is formed therebetween in the intermediate section of chute 55. The heat generated by this are impels the arc upwardly in chute 55, and the blowout assembly described above furnishes additional impelling force. As shown in Figs. 8 and 9, the arc in moving upward first impinges on conductive member 58a between contact II and member 56a, and as contact 12 continues to move, the arc is extended until it impinges on member 581). At this time, the arc will exist in the form of short are 8| between contact I and member 58a, another short are 62 between adjacent leg portions of members 58a and 58b, and another short are 83 formed between member 5821 and contact i2. Continued movement of contact l2 causes the arc to successively impinge on the succeeding conductive members 58c, 5811. 58c, 51 thereby successively drawing a plurality of short arcs between adjacent leg portions of adjacent conductive members. These short arcs rise in chute 55 and the arc current between the plurality of short arcs traverses the leg portions and curved portions of conductive members 58. As the short arcs move toward the exhaust section of the chute, the distance between adjacent leg portions of adjacent members 58 increases, thereby increasing the resistance of the air gaps through which the short arcs travel, and hence reducing the magnitude of the arc current and hastening the extinction of the arc. In addition, the arc current flowing in the conductive leg portions meets a path of continually increasing resistance owing to the increasing distance in the conductive members through which this current must flow. This increasing resistance further progressively reduces the arc cur-' rent and thereby further speeds the extinction pinging on leg portions 6|, 62 cause a current to flow therein, for example downwardly in leg 62, as indicated by arrow 86, and upwardly in le 6|, as indicated by arrow 81. sented by arrow 86 produces about leg 62 a field represented by flux line 88, while the current represented by arrow 81 produces about leg 6| a field represented by fiux line 89. The field represented by flux line 88 acts on the short are existing between leg 62 of member 58b and the adjacent leg of member 58a and forces this short are upward toward the exhaust section of the chute. Likewise the field represented by flux line 89 forces the short are existing between leg 6| of member 581) and the adjacent leg-portion of member 580 toward the exhaust section of the chute. This blowout action produced by the arc current traversing members 58 considerably.

hastens the travel of the arc toward the exhaust section of the chute where the arc is eventually extinguished.

When the short arcs are in the intermediate section 53 of the chute, only the members 58 of side wall 51 are effective in extinguishing the arc. haust section of the chute, the arcs encounter the leg portions of conductive members 59, which increase in depth in a direction toward side wall adjacent leg portions of members 59a, 58b. The.

are current now flows through member 5911 and produces magnetic fields about the legs of this member similar to those produced by the are current in member 58b tending to extinguish the arc. The action of the other members 59 as the The current repre However, when the arcs approach the ex-' shorter arcs reach the exhaust section of the chute is similar to that described above for member 59c andthe combined field. produc d by e current in all of the members, 5.8.-.. 59 is now increased with respect to, the field produced when the arc current traversed only members 58, thereby greatly speeding the extinction of the arc in the exhaust section of the chute.

Although in the above described operation 02 the arc chute, it was assumed that the. are impinged on member 58a upon separation of contacts ll, l2, it will be readily apparent that the arc might impinge on member 59a upon separation of the contacts and then be caused to successively impinge on members 59b, 59c, 59d, 59e, 59f, without changing the principle of operation of the arc extinguishing means.

In the alternate embodiment of the U-shaped conductive member illustrated in Fig. '7, the leg portions 93, 94 of the member extend substantially parallel to each other from the bight of the U to the exhaust section of the chute. The operation of arc chute provided with conductive members of the type shown in Fig. 7 is identical to that above described with respect to the arc chute illustrated in Figs. 1 to 6.

Although but two embodiments of the invention has been shown and described, it will be apparent to those skilled in the art that various modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

t is claimed and desired to secure by Letters Patent:

1. Means for extinguishing an electric arc movable in a predetermined direction comprising an arc chute provided with a pair of spaced side walls located on opposite sides of the path of movement of said arc and having an intermediate section wherein said arc is formed and an exhaust section, and a plurality of U-shaped conductive members on which difierent portions of said are successively impinge, said members being secured to said side walls and forming two interleaved rows disposed in the general lengthwise direction of said arc, each said member comprising a pair of spaced leg portions extending in the general direction of movement of said arc and having a curved portion joining said leg portions in said intermediate section of said chute, each of said leg portions of each of said members abutting one of said walls in said intermediate section of said chute and increasing in depth in a direction perpendicular to said directions from said intermediate section to said exhaust section.

2. Means for extinguishing an electric arc movable in a predetermined direction comprising an arc chute provided with a pair of spaced side walls located on opposite sides of the path of movement of said are and having an intermediate section wherein said arc is formed and an exhaust section, and a plurality of U-shaped conductive members on which different portions of said are successively impinge, said members being secured to said side walls and forming two interleaved rows disposed in the general lengthwise direction of said arc, each said member comprising a pair of spaced leg portions extending in the general direction of movement of said are and having a curved portion joining said leg portions, the distance between adjacent leg portions of adjacent members increasing from said intermediate section of said exhaust section, each of said leg portions of each of said members 6 abutting one of said walls/in, said intermediate: section of said chute. and increasing in. depth in; a direction perpendicular to said directions from said intermediate section to, said exhaust sec tion.

3. Means. for extinguishing anv electric arc movable. in a. predetermined direction. comprise. ing anarcv chute. provided. withla, pair of spaced side walls located on opposite sides of the. pathv of movement of said are and having. an inter.- mediate section wherein said are is. formed; and an exhaust, section, and a plurality of U-shaped conductive members on which different portions of said arc successively impinge, said members being secured to said side walls and forming two interleaved rows disposed in the general lengthwise direction of said arc, each said member comprising a pair of spaced leg portions extending in the general direction of movement of said are and having a curved portion joining said leg portions in said intermediate section of said, chute, the said members secured to one of said walls abutting said one wall in said intermediate section and increasing in depth in a direction toward the opposite said wall in said intermediate section of said chute and abutting said opposite wall at said exhaust section of said chute.

4. Means for extinguishing an electric arc movable in a predetermined direction comprising an arc chute provided with a pair of spaced side walls located on opposite sides of the path of movement of said arc and having an intermediate section wherein said arc is formed and an exhaust section, and a plurality of U-shaped conductive members on which different portions of said arc successively impinge, said members being secured to said side walls and forming two interleaved rows disposed in the general lengthwise direction of said arc, each said member comprising a pair of substantially parallel spaced leg portions extending in the general direction of movement of said are and having a curved portion joining said leg portions in said intermediate section of said chute to form a U, the said members secured to one of said walls abutting said one wall in said intermediate section and increasing in depth in a direction toward the opposite said wall from the bight of said U and abutting the opposite said wall at said exhaust section of said chute, the said members secured to one of said walls being staggered with respect to the said members secured to the other said wall in said intermediate section of said chute and said members secured to said one wall overlapping said members secured to said other wall in said exhaust section of said chute.

5. Means for extinguishing an electric arc movable in a predetermined direction comprising an arc chute provided with a pair of spaced side walls located on opposite sides of the path of movement of said arc and having an intermediate section wherein said arc is formed and an exhaust section, and a plurality of U-shaped conductive members on which different portions of said are successively impinge, said members being secured to said side Walls and forming two interleaved rows disposed in the general lengthwise direction of said arc, each said member comprising a pair of spaced leg portions extending in the general direction of movement of said are and having a curved portion joining said leg portions in said intermediate section of said chute to form a U, each of said members secured to said walls abutting said one wall in said intermediate section and increasing in depth in'a di- REFERENCES CITED rection toward the opposite said wall from'the bight of Said U and abutting the Opposite Said The following references are of record in the wall at said exhaust section of said chute, the file of this patent:

said members secured to one of said walls being 5 staggered with respect to the said members se- UNITED STATES PATENTS cured to the other of said walls in said inter- Number Name Date mediate section of said chute and said members 2,353,729 Jensen July 18, 1944 secured to said one wall overlapping said mem- 2,356,040 Ellis et a1. Aug. 15, 1944 bers secured to said other wall in said exhaust 10 2,408,352 Titus Sept. 24, 1946 2,477,189 Lerstrup July 26, 1949 section of said chute.

1 ALVIN E. HERMAN. 

